Question

A transverse section of the trunk of a tree shows concentric rings which are known as growth rings. How are these rings formed? What are the significance of these rings?

Answer 1

1. Growth (or) Annual Rings:In the spring season cambium is very active and produces large number of xylary elements called Earlywood or Springwood. In the Winter season - cambium is less active and form few xylary elements - Latewood or Autumn Wood.
2. The springwood is lighter in color and has a lower density whereas the autumn wood is darker and has a higher density. The annual ring denotes the combination of earlywood and latewood and the ring becomes evident to our eye due to the high density of latewood. Sometimes annual rings are called growth rings.
3. Pseudo – Annual Rings: Additional growth rings are developed within a year due to adverse natural calamities like drought, frost defoliation, flood, mechanical, injury and biotic factors. Such rings arc called pseudo – or false – annual rings.
4. Dendrochronology:
   Each annual ring corresponds to one year’s growth and on the basis of these rings, the age of a particular plant can easily be calculated. The determination of the age of a tree by counting the annual rings is called dendrochronology.